Compositional Evolution of Zoned Tourmaline Crystals from Pockets in Common Pegmatites of the Moldanubian Zone, Czech Republic
Bibliographic record
Abstract
Common pegmatites commonly occur in migmatized biotite-sillimanite gneisses and felsic granulites of the Strazek Unit, Moldanubian Zone, in the Czech Republic. Mostly concordant dikes or irregular bodies consisting of an outer granitic unit, a graphic unit and a pocket unit with large crystals (up to 1 m long) of minerals show transitional to locally sharp contacts to the host migmatized rocks. Thin muscovite-rich veins with the assemblage muscovite, albite, quartz and tourmaline are closely associated spatially. Variable prismatic to lens-shaped tourmaline crystals and their aggregates, up to 30 cm across, from pockets and muscovite-rich veins exhibit striking zoning in the optical microscope and in BSE images: core (foitite-schorl-magnesio-foitite), intermediate zone (schorl-dravite) and narrow outer rim (schorl-dravite); tourmaline from muscovite veins is relatively homogeneous (dravite-magnesio-foitite). A slight decrease in X-site vacancy, in Fe-tot/(Fe-tot + Mg) and Al contents but sharp increase of Ti from the core to intermediate zone and outer rim, respectively, are typical. Nearly all Fe was determined as Fe2+ (3% of Fe3+ in both core and intermediate zones of the tourmaline) using Mossbauer spectroscopy. The mineral assemblages (andalusite + cordierite) of common pegmatites and their geological and petrographic features indicate P-T conditions of similar to 500-650 degrees C and less than similar to 3-4 kbar for massive units, but lower for tourmalines and other minerals from pockets and in particular for associated muscovite-rich veins. The distribution of pegmatites in migmatitic rocks, their concordant and transitional (diffusive) contacts to the country rocks, simple assemblages of minerals, primitive chemical composition of minerals (all typical for abyssal pegmatites), and common large pockets lined with well-developed crystals of smoky quartz, feldspars, muscovite, and tourmalinedo not fit the current classifications of granitic pegmatites.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".